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SPC using I-MR

Discussion in 'SPC - Statistical Process Control' started by amostafa, Oct 22, 2016.

  1. amostafa

    amostafa New Member

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    Dears,
    I started the SPC using MINITAB. I used the I-MR (individual/moving range chart). which chart should be considered first? (i.e sometimes out of control point appears in individual chart but none appearing in the corresponding moving range chart; and vice versa). Is it necessary for the OOC points to be detected in both charts to tell that process is out of control?
     
    amostafa, Oct 22, 2016
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  2. Bev D

    Bev D Moderator Staff Member

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    To answer your direct question: no. An out of control condition does not have to appear in both charts. In fact it often won't. The two charts (even an I, MR chart) plot different aspects process variation.

    I suggest reading the works of Donald Wheeler. He has published many articles on SPC. His recent articles can be found at Quality Digest. You can search for him and then select "Author Archive" to see a list of all of his articles. I suggest going to the end of the list and start reading there. Many of this most recent articles are on general statistical concepts...

    You can also go to SPC Press to see many of his older articles.
     
    Bev D, Oct 22, 2016
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